Geothermal ground source/water source heat exchange systems typically include closed loops of tubing that are buried in the ground, or submerged in a body of water. Fluid is circulated through the loops of tubing so that the fluid either absorbs heat from or rejects heat into the naturally occurring geothermal mass and/or water surrounding the tubing. The ends of the tubing loop extend to the surface and are fluidly coupled to an interior air heat exchanger. The naturally warmed or cooled fluid is circulated through the interior air heat exchanger to warm or cool an interior space.
Common and older geothermal water-source heating/cooling systems typically have a pump for circulating a fluid comprised of water, or water with anti-freeze, in plastic (typically polyethylene) underground geothermal tubing so as to transfer geothermal heat to or from the ground in a first heat exchange step. In a second heat exchange step, a refrigerant heat pump system transfers heat to or from the water. Finally, in a third heat exchange step, an interior air handler (comprised of finned tubing and a fan) transfers heat to or from the refrigerant to heat or cool interior air space.
Newer design geothermal DX heat exchange systems have only two heat exchange steps. DX systems typically have refrigerant fluid transport lines placed directly in the sub-surface ground and/or water. The sub-surface refrigerant lines are typically comprised of copper tubing. A refrigerant fluid, such as R-22, or the like, is circulated through the lines to transfer geothermal heat to or from the sub-surface elements in a first heat exchange step. DX systems only require a second heat exchange step to transfer heat to or from the interior air space, typically by means of an interior air handler. Consequently, DX systems use fewer heat exchange steps and do not require power to run a water pump, and therefore are generally more efficient than water-source systems. Further, since copper is a better heat conductor than most plastics, and since the refrigerant fluid circulating within the copper tubing of a DX system generally has a greater temperature differential with the surrounding ground than the water circulated through the plastic tubing of a water-source system, generally, less excavation and drilling is required, thereby decreasing installation costs.
While most in-ground/in-water DX heat exchange designs are feasible, various improvements have been developed to enhance overall system operational efficiencies. Several such design improvements, particularly in direct expansion/direct exchange geothermal beat pump systems, are taught in U.S. Pat. No. 5,623,986 to Wiggs; U.S. Pat. No. 5,816,314 to Wiggs, et al.; U.S. Pat. No. 5,946,928 to Wiggs; and U.S. Pat. No. 6,615,601 B1 to Wiggs, the disclosures of which are incorporated herein by reference. Such disclosures encompass both horizontally and vertically oriented sub-surface heat geothermal heat exchange means.
Conventional DX system typically heat or cool at least one control medium. A control medium could be, for example, water, water and/or antifreeze, a solid (such as concrete), or a vapor (such as air in an interior room). In a conventional DX system design, the control medium is air in an interior space, and the sub-surface geothermal heat exchange tubing provides heat to the interior air by means of an interior air-handler. In a conventional DX system design, the system is used to either heat or cool, but is not designed to simultaneously heat and cool different control media or similar control media located in different interior spaces.
It is advantageous to maintain or increase the operational efficiencies of a DX system. The subject matter disclosed herein primarily relates to various improvements that will maintain or increase system operational efficiencies